1. Field of the Invention
The present invention relates to an apparatus for sampling, for quality inspection purposes, a small number of printed sheets (e.g. 2 printed sheets) from a printed sheets line in a conveyance path along which folded printed sheets are conveyed to a counter stacker or the like in a line overlapping each other at certain pitches.
2. Description of the Related Art
Conventional apparatuses for sampling a small number of printed sheets from a printed sheets conveyance line are disclosed in, for example, Japanese Patent Publication (kokoku) Nos. 55-31070, 55-31069, and 55-5466.
The apparatus disclosed in Japanese Patent Publication No. 55-31070 includes: an opening portion formed on one side of the rising section of a conveyance path for conveying printed sheets from the folder unit of a rotary press to a counter stacker or the like; a sampling plate located in the vicinity of the conveyance path and angularly displaced by first driving means to thereby advance into the conveyance path from behind the opening portion; a capture portion located at the tip portion of the sampling plate for capturing a small number of printed sheets from a line of printed sheets conveyed along the conveyance path when the sampling plate advances into the conveyance path; an ejection palate located opposite the sampling plate with respect to the conveyance path for ejecting the sampled printed sheets onto a receiver; and second driving means for angularly displacing the sampling plate beyond the side of the printed sheets line after completion of the sampling.
In the apparatus, the sampling plate stands by in the vicinity of a line of printed sheets, which are conveyed from the folder unit of the rotary press and overlap each other at certain pitches. In response to a manually issued sampling instruction, the sampling plate is angularly moved by the first driving means via a driving shaft to thereby advance into the printed sheets line. Thus, when the leading ends of a small number of printed sheets enter the capture portion, advancement of the printed sheets is prevented. Subsequently, the captured printed sheets are separated from the printed sheets line.
The thus-sampled printed sheets stand stationary in a curved shape. Meanwhile, when the sampling plate advances into the printed sheets line, a limit switch goes ON to generate an electric signal. The electric signal triggers the counting of pulses of an electric pulse signal output at a rate corresponding to the printing speed of the rotary press. When the number of counted pulses reaches a preset pulse number--which corresponds to a travel distance of the printed sheets equal to a length of a single printed sheet, a counting end signal is issued. In response to the counting end signal, the sampling plate is angularly displaced laterally to eject sampled printed sheets and avoid interference with a line of printed sheets conveyed along the conveyance path. Then, the sampling plate retreats to its standby position. The above-described preset pulse umber is determined by converting a preset travel distance of a printed sheet (the length of a printed sheet) into a corresponding number of pluses that are output at a rate corresponding to the printing speed of the rotary press.
According to the apparatus disclosed in Japanese Patent Publication No. 55-31069, an opening portion is provided on one side of the rising section of a conveyance path for conveying printed sheets from the folder unit of a rotary press to a counter stacker or the like. After first sampling member is advanced into a printed sheets line, second sampling member, which is located upstream of and operates independently of the first sampling member, is plunged into the printed sheets line to thereby sample a small number of printed sheets through the opening portion. Upon completion of the sampling, the first and second sampling members retreat in a manner to avoid interference with the printed sheets line.
A contactor for operating a limit switch for detecting the leading end of first printed sheet subsequent to printed sheets to be sampled is projected at a predetermined position of the conveyance path located downstream of a predetermined plunge position of the second sampling member, whereby it is readied to detect the leading end of the subsequent printed sheet. A preset distance is defined as a distance obtained by subtracting half of an overlap pitch of printed sheets from the distance between the position of the contactor and the predetermined plunge position of the second sampling member. The preset distance is then converted into a corresponding number of pulses that are output at a rate corresponding to the printing speed of a rotary press. As soon as a sampling start button is pressed ON to advance the first sampling member, counting of pulses of the electric pulse signal starts in order to calculate the travel distance of a printed sheet from the counted number of pulses. When the number of counted pulses reaches a number of pulses corresponding to the operating time of the second sampling member, the counting is halted. Then, when a detection signal is issued from the limit switch, the counting resumes for counting the rest of the set number of pulses. Upon completion of counting of the set number of pulses, the second sampling member is instructed to plunge into a printed sheets line.
The apparatus disclosed in Japanese Patent Publication No. 55-5466 includes first sampling member and second sampling member located downstream of the first sampling member. The first sampling member moves between a standby position located away from the printed sheets line and an operation position, where part of a printed sheets line conveyed along the conveyance path extending between the folder unit of a rotary press and a counter stacker or the like is floated from the conveyance path, so that the printed sheets line is branched. The second sampling member moves between a standby position located away from the printed sheets line and an operation position, where the second sampling member interferes with a required number of printed sheets present downstream in the branched line so as to eject the sampled printed sheets to the exterior of the printed sheets line.
When the first sampling member is angularly displaced into the printed sheets line in response to a manually issued sampling instruction, counting of pulses of an electric pulse signal output at a rate corresponding to the printing speed of a rotary press starts for calculating the travel distance of a printed sheet along the conveyance path from the counted number of pulses. When the number of counted pulses reaches a predetermined pulse number, which has been predetermined through correction for following the printing speed of a rotary press, the second sampling member is plunged into the printed sheets line so as to eject printed sheets to be sampled into an ejection section.
The above-described conventional apparatuses for sampling a small number of printed sheets from a printed sheets conveyance line involve the following problems.
In the apparatus disclosed in Japanese Patent Publication No. 55-31070, when a sampling instruction is manually issued for sampling (hereinafter may be referred to as "inspecting" or "inspection" or "to inspect") printed sheets, the sampling plate having the capture portion immediately advances angularly into the printed sheets line. To sample, for example, two printed sheets for inspection, the length of the sampling plate as measured along a conveyance direction is set to double the aforementioned overlap pitch, assuming that the overlap pitch of printed sheets remains unchanged.
However, the overlap pitch of printed sheets varies due to a disturbance of printed sheets discharged from the folder unit or a disturbance of printed sheets during conveyance. In addition, the operation of the sampling plate is not controlled such that the sampling plate advances into a printed sheets line, which is conveyed at a rate corresponding to a printing speed, at an optimum position of the line. In other words, no specific relation is established between printed sheets to be sampled and the position on a printed sheets line where the capture portion of the sampling plate, which immediately operates in response to a sampling instruction, advances. Thus, the position where the capture portion advances into the printed sheets line is unknown. That is, since means for monitoring an overlap pitch of printed sheets along the conveyance path is not provided, the sampling plate may advance into a line of printed sheets conveyed at nonuniform overlap pitches. In such a case, the sampling plate advances into a printed sheets line at a position inadequate for sampling target printed sheets.
Specifically, the sampling plate, which has the capture portion and advances into a printed sheets line in an angularly displacing manner, advances into the line regardless of the position of the leading end of a printed sheet. As a result, the sampling plate may thrust the leading end of the printed sheet away, cause printed sheets to be folded, block the conveyance of printed sheet, or bite printed sheets, resulting in a disturbance of the flow of the printed sheets line. This in turn may cause a paper jam in the conveyance path.
Also, as soon as the sampling plate is angularly displaced, the ejection plate is angularly displaced in a substantially oblique upward direction, thereby defining a space having a V-shaped cross-section with the sampling plate. For example, two printed sheets captured in this space are separated from the printed sheets line, so that the printed sheets stand stationary in a curved shape. Immediately after the capture portion of the sampling plate advances into a printed sheets line, the limit switch operates to generate an electric signal, which initiates the counting of electric pulses. Upon completion of the counting, a signal indicative of the completion of the counting causes the ejection plate to be angularly displaced downward, and causes the sampling plate having the capture portion to be angularly displaced laterally to a position where the sampling plate does not interfere with a printed sheets line.
Then, a force causing sampled printed sheets to be curved is released. As a result, the sampled printed sheets tend to restore themselves to a straight position due to a restoring force, particularly when the number of pages is relatively large. The leading ends of the thus restored sampled printed sheets tend to touch the contact portion between a roller located above the opening portion and a printed sheets line conveyed along the roller, to thus be caught turbulently in the contact portion, i.e. in the conveyance path. In addition, for example, in the case of a newspaper rotary press which prints at least 120,000 copies per hour, since the tail ends of the curved printed sheets are in contact with a conveyor belt or a conveyor roller located under the opening portion, the tail ends are flipped by the conveyor belt or conveyor roller. This involves a problem that the thus-flipped tail ends advance ahead of the leading ends, causing turbulence in conveyance of the sampled printed sheets.
Further, the sampling plate is angularly displaced; i.e. moves along a circular path, to advance into a printed sheets line. This arrangement involves a problem that the optimum position and depth of advancement of the capture portion with respect to a printed sheets line vary with the overall thickness of printed sheets or the thickness of a printed sheets line, which varies with the number of pages of the printed sheets.
In the apparatus disclosed in Japanese Patent Publication No. 55-31069, as in the one disclosed in Japanese Patent Publication No. 55-31070, when a sampling start button is pressed ON, the first sampling member is angularly displaced along a circular path to advance into a printed sheets line without consideration of disturbance or variation in the printing speed or the overlap pitch of printed sheets. That is, the first sampling member is plunged into the printed sheets line regardless of the positions of printed sheets or the overlap pitches of the printed sheets in the printed sheets line, involving a potential disturbance of the printed sheets line or a potential failure to advance into the printed sheets line at a position adequate for sampling. As a result, as in the apparatus disclosed in Japanese Patent Publication No. 55-31070, the first sampling member may thrust printed sheets away, cause printed sheets to be folded, or bite printed sheets, resulting in a disturbance of the flow of the printed sheets line. This in turn may cause a paper jam in the conveyance path.
Also, for example, when two printed sheets are to be inspected, the contactor for operating the limit switch for detecting the leading end of first printed sheet subsequent to the two printed sheets is projected in preparation for detecting the leading end of the subsequent first printed sheet. The preset distance is defined as a distance obtained by subtracting half of an overlap pitch of printed sheets from the distance between the position of the contactor and the predetermined plunge position of the second sampling member. The preset distance is determined by converting the present distance into a corresponding number of pulses that are output at a rate corresponding to the printing speed of a rotary press. As soon as the sampling start button is pressed ON to advance the first sampling member, counting of pulses of the electric pulse signal starts in order to calculate the travel distance of a printed sheet from the counted number of pulses. When the number of counted pulses reaches a pulse number corresponding to the operating time of the second sampling member, the counting is halted. Then, when a detection signal is issued from the limit switch, the counting resumes for counting the rest of the set number of pulses. Upon completion of counting of the set number of pulses, the second sampling member is instructed to plunge into a printed sheets line so as to eject the printed sheets from the printed sheets line.
That is, when the sampling start button is arbitrarily pressed ON, the first sampling member is immediately operated without consideration of the positions of printed sheets. Thereafter, upon completion of counting of the rest of the set number of pulses after a signal is received from the limit switch for detecting the leading end of a printed sheet, the second sampling member is plunged into a printed sheets line. In other words, the plunging operation of the second sampling member is initiated in accordance with a predetermined operational relation with the leading end of a printed sheet which has caused the limit switch to operate. However, since the overlap pitches of printed sheets in a printed sheets line are not monitored, and the second sampling member is plunged into a printed sheets line without adjustment of its operational relation with printed sheets to be sampled, the second sampling member frequently plunges into a printed sheets line having irregular overlap pitches of printed sheets. In addition, as in the case of the first sampling member, the second sampling member plunges into a printed sheets line at a position inadequate for sampling target printed sheets. As a result, the flow of the printed sheets line is disturbed, or such a plunge damages printed sheets.
Further, the limit switch for detecting the leading end of first printed sheet subsequent to target printed sheets includes a paper guide which also serves as a protector for the contactor of the limit switch. The paper guide is attached indirectly to a shaft for angularly displacing the first sampling member. Accordingly, this arrangement involves a problem that as soon as the first sampling member operates, the paper guide presses a printed sheets line via the first sampling member to interfere with the movement of the printed sheets line, resulting in a disturbance of the flow of the printed sheets line.
The apparatus disclosed in Japanese Patent Publication No. 55-5466 functions in the following manner. When the first sampling member is angularly displaced into the printed sheets line in response to a manually issued sampling instruction, counting of pulses of an electric pulse signal output at a rate corresponding to the printing speed of a rotary press starts for calculating the travel distance of a printed sheet along the conveyance path from the counted number of pulses. When the number of counted pulses reaches a predetermined number of pulses, which has been predetermined through correction for following the printing speed of a rotary press, the second sampling member is plunged into the printed sheets line so as to eject printed sheets to be sampled into an ejection section.
That is, as in the apparatus disclosed in Japanese Patent Publication No. 55-31069, the first and second sampling members are advanced into a printed sheets line without monitoring of overlap pitches of printed sheets in the printed sheets line and without adjustment of their operational relation with printed sheets to be sampled. As a result, the first and second sampling members frequently advance into a printed sheets line having irregular overlap pitches of printed sheets. In addition, the first and second sampling members advance into a printed sheets line at a position inadequate for sampling target printed sheets. Consequently, printed sheets are damaged, the flow of a printed sheets line is disturbed, or the conveyance path is jammed with printed sheets.